I have prepared an azo dye with orange colour in polar solvents. As is seen in the absorption spectra, absorption is in the UV region and up to around 400 nm in the visible. However, an orange colour solution typically shows absorbance in the 500-600 nm range. This dye also shows a green specular reflectance in a dry solid form. Could anyone please explain the possible reasons for these two phenomena?
The peak of the absorption spectrum is at 361 nm, which is in the UV, but there is nonzero absorbance at wavelengths between 400 and 500 nm, which is in the visible. The visible light absorbance spectrum is dominated absorbance at the shorter (violet) wavelengths, which gives a yellow color, with just enough of the blue wavelength absorbance to give it an orange color.
The compound may be fluorescent, which could account for the green color, since fluorescence emission is at a longer wavelength than absorbance.
According to your spectrum, there is a weak absorbance between 400 and 500 nm (absorbed color is blue-cyan), which gives an orange reflected color (complementary color).
Colours of subjets ariund us depend on the spectral ability their surfaces to reflect light which they are illuminated. For example if white light do not reflectedat all sublect is transparent and no colour You can see. In opposite black colour arise when all illuminated light get absorbed. You case has described in this model frame Neil Ladhary 5 hours ago.
Thank you for your answers. Yes,I see the absorbance in the 400-500 nm and now it makes sense why the dye looks orange.
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